Friday, 4 January 2008

Mystery mechanism heals high-tech composite

Engineers have high hopes for composite materials that can repair small cracks in their structure. "When you have any damage induced by fatigue, there's usually nothing you can do except wait for catastrophic failure," says Jeffrey Moore, who led the research at the University of , Urbana, US.

Self-healing composites should change that. These materials contain capsules of a liquid adhesive which leaks out and repairs tiny cracks when they appear. (Watch a video showing how these materials might repair helicopter blades. Animation by the Beckman Institute Imaging Technology Group)

However, the adhesives usually require some kind of post-processing to make them set, such as curing with UV light or heating to high temperatures. What engineers would prefer, though, is a material that healed itself without any extra intervention.

In 2001, Moore's group developed just such a material that relied on the mixing of two different chemicals that set like a two-part epoxy.

The material contains two types of capsule: one containing a ring hydrocarbon called dicyclopentadiene and the other containing a ruthenium solvent that acts as a catalyst, causing the rings to break open and polymerise. Any crack causes the chemicals to mix and set, bonding the crack faces together.

But ruthenium is rare and that makes it impractical for most applications, so his team set to work looking for an alternative.

To their surprise, it worked almost as well. Moore says the solvent was probably dissolving the composite material, allowing it to mix and bond again, although he concedes the exact mechanism remains a mystery.

The group then tested another solvent, using a chemical called chlorobenzene. After fracture and self-healing, the composites containing chlorobenzene recovered up to 100% of their original strength – as good as new.

And, although toxic, chlorobenzene is a hundred times cheaper than ruthenium and is much more easily available.

However, Bond warns that the toxicity of chlorobenzene is likely to make the idea less industrially attractive. Moore's team, meanwhile, is testing a number of less toxic, more biodegradable solvents to do the same job.

Flexible-jointed robot is no pushover

If robots are going to work alongside humans, then they will need to stand up to accidental bumps and shoves, not to mention the occasional deliberate kick. (lol, on the deliberate kick )

That is why researchers in Japan have developed software that allows a life-size humanoid robot to stay on its feet no matter where on its body it is pushed. Theirs is the first full-size humanoid to show such steadiness – others of similar size inevitably topple over when nudged in the right spot. In experiments, the robot was subjected to repeated pushes. A virtual robot received much harder shoves.

Rebalancing should allow humans to interact more naturally with robots, letting them act as a physical guide, for example. If a controller tries to show other full-size humanoids how to perform a task by moving its limbs, there is a strong chance the thing will fall over.

The robot's balancing ability depends on its joints. For one thing they are never kept rigid, even when standing still, meaning they yield slightly when the robot is pushed.

Force sensors within each joint also work out the position and velocity of the robot's centre mass as it moves around. Control software rapidly figures out what forces the robot's feet need to exert on the ground to bring it back into balance, and tells the joints how to act.

As well as keeping the robot steady as it moves itself around, the technique lets it readjust to sudden, external forces.

In cases when the robot's joints cannot quickly swing its centre of mass back into place, it ends up staggering – a bit like a boxer after a heavy punch. This constitutes several rounds of rebalancing, with each cycle shifting the centre of mass closer to its original balance point.

Some other humanoid robots rebalance themselves by measuring changes to the position of each joint. This requires very accurate knowledge of the magnitude of an applied shove, says ATR researcher Sang-Ho Hyon, which is difficult to achieve without covering the whole robot with force sensors.

Most robots lack such sensors, and so use a relatively simple trick to rebalance themselves. For example, Honda's ASIMO, shifts its hip joint in order to stay steady, which only works in some cases.

"This team is currently ahead of the pack in terms of having it work on a full robot," Pratt told New Scientist. "Making the robot more compliant instead of stiff plays a big part in that," he says, and the ability to measure and control the torque force at every joint is also crucial.

Pratt and colleagues are working on their own control strategy, which involves rebalancing with a single step. "Imagine you are crossing a pond and you can only step to one rock to rebalance," he says. The software will be tested next year after the team finishes building a suitable humanoid.

Androids in pain and breast-feeding baby bots

Japan's premier robot event offers visitors the chance to find a high-tech ping-pong opponent, see an android dental patient twitch in pain, and to nurse baby robots in the same afternoon.

Showcasing around 1000 industrial and service robots, the International Robot Exhibition in Tokyo confirmed Japan's enthusiasm for robots, many of which manufacturers hope to adapt to the needs of an ageing population.

Employees of Yamazaki Educational Systems, for example, were busy nursing four baby robots who cried and burped enthusiastically. The $620 robots are meant to help teach soon-to-be parents how to care for infants.

"Opportunities to see kids in society are decreasing," says company representative Kaoru Nukui, referring to the sharp fall-off in births in Japan that means many families have only one child.

"The way students would touch a baby would be completely different once they have looked, touched, and experienced this 'baby'," he adds, before demonstrating a nipple-like sensor that can be used to "breast feed" each baby.

Nearby, a female android on a dentist's chair also drew the crowds. Simroid, a $635,000 android, was developed by Japanese company Kokoro as a dummy patient for dental students. See a video of Simroid in action here.

"That's painful!" Simroid says, twitching and blinking when a student pressed her teeth too hard with a tool. Her chest also rose and fell as if she was breathing.

My comment: I think the key to involve the technology all those institutes develop is to make it useful and practical. And here we have 3 examples for very practical devices. The problem with robots is that they are too far from a normal human environment-here we saw people are succeeding to change that. And the self-healing composite is absolute yayness. It's simply awesome. I guess there is much more to be done until we see it in everyday use, but just think how many catastrophes can be avoided with it. That's what this blog is! To report such awesome discoveries!

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